Magnetic audio recording tape and method of preparation thereof

Abstract

An audio magnetic recording medium includes a magnetic material carrier backing and a layer of a magnetic material thereover comprising magnetic particles dispersed in a binder, the magnetic particles having a thin coating thereon of a rare earth-containing material, preferably samarium pentoxide. The amount of the rare earth-containing material in the recording medium is only a small percentage by weight of the coated magnetic particles so as not to adversely effect the erasability of the magnetic record to be recorded, but is of sufficient amount to improve the frequency response, signal to noise ratio, or channel separation characteristics thereof.

I claim: 
     
       1. In an audio magnetic recording medium including a magnetic material carrier backing and a layer of a magnetic material thereover comprising magnetic particles dispersed in a binder, the improvement wherein the magnetic particles have a thin coating thereon of a rare earth-containing material, the amount of the rare earth-containing material in said recording medium being only a small percentage by weight of the coated magnetic particles so as not to adversely affect the erasability of the magnetic record to be recorded, but being of sufficient amount to improve the frequency response, signal to noise ratio, or channel separation characteristics thereof. 
     
     
       2. The magnetic recording medium of claim 1 wherein said rare earth-containing material includes samarium. 
     
     
       3. The magnetic recording medium of claim 1 wherein said rare earth-containing material is samarium pentoxide. 
     
     
       4. The magnetic recording medium of claim 1, wherein the amount of the rare earth-containing material in said layer is no more than about 2% of the weight of the coated magnetic particles therein. 
     
     
       5. The magnetic recording medium of claim 2, wherein the amount of the rare earth-containing material in said layer is no more than about 2% of the weight of the coated magnetic particles therein. 
     
     
       6. The magnetic recording medium of claim 3, wherein the amount of the rare earth-containing material in said layer is no more than about 2% of the weight of the coated magnetic particles therein. 
     
     
       7. The magnetic recording medium of claim 1, wherein the amount of rare earth-containing material in said layer is less than about 1% of the weight of the coated magnetic particles therein. 
     
     
       8. The magnetic recording medium of claim 2, wherein the amount of samarium-containing material in said layer is less than about 1% of the weight of the coated magnetic particles therein. 
     
     
       9. The magnetic recording medium of claim 3, wherein the amount of samarium pentoxide in said layer is less than about 1% of the weight of the coated magnetic particles therein. 
     
     
       10. The magnetic recording medium of claim 1, wherein the amount of the rare earth-containing material in said layer is about 0.5% of the weight of the coated magnetic particles. 
     
     
       11. The magnetic recording medium of claim 2, wherein the amount of the samarium-containing material in said layer is about 0.5% of the weight of the coated magnetic particles. 
     
     
       12. The magnetic recording medium of claim 3, wherein the amount of the samarium pentoxide in said layer is about 0.5% of the total weight of the coated magnetic particles. 
     
     
       13. A method for making an improved erasable grain-oriented magnetic audio signal recording medium, the method comprising the steps of mixing relatively small amounts of a rare earth-containing powder with a powdered magnetic material so that the rare earth-containing material is no more than about 2% by weight of the coated powder mixture and so that the rare earth-containing powder is a coating on the particles of the powdered magnetic material, coating a length of a non-magnetic carrier with said powder mixture and a hardenable binder therefor which adheres the powder mixture particles to each other and to said carrier surface, applying a magnetic field to said coating to orient said coated particles, and hardening said binder to fix the orientation of said coated particles. 
     
     
       14. The method of claim 13 wherein said rare earth-containing material includes samarium. 
     
     
       15. The method of claim 13 wherein said rare earth-containing material is samarium pentoxide. 
     
     
       16. The method of claim 13 wherein the amount by weight of the rare earth-containing material in proportion to the weight of the coated magnetic particles is no more than about 2%. 
     
     
       17. The method of claim 13 wherein the amount by weight of the rare earth-containing material in proportion to the weight of the coated magnetic particles is less than about 1%. 
     
     
       18. The method of claim 13 wherein the amount by weight of the rare earth-containing material in proportion to the weight of the coated magnetic particles is about 0.5%. 
     
     
       19. The method of claim 13 further including the step of calendering said coated carrier, and wherein said step of applying a magnetic field is performed both before and after said calendering step.